Field of the Invention
The present invention relates to a connector terminal including an elastic contact piece having a contact portion through which the elastic contact piece contacts a cylindrical terminal.
Description of the Related Art
A kind of electrical connector (such as a connector to be equipped in a glow plug acting as an ignitor or a pre-heating plug in an engine, and a connector used for connecting a combustion pressure sensor to a wire harness) includes a cylindrical male connector. Since the male connector is designed to be rotation-symmetric with a female connector, the male connector can be fit into the female connector, even if the male connector is caused to rotate around an axis thereof in either direction. Accordingly, the male connector can be readily fit into the female connector, even if the connectors are manually handled in the darkness.
The electrical connector as mentioned above generally includes an elastic contact piece having a contact portion through which the elastic contact piece contacts the cylindrical terminal.
FIG. 32 is a perspective view of a conventional electrical connector disclosed in Japanese Patent Application Laid-open on No. 1997-35825.
The illustrated electrical connector includes a plug connector 1000 and a receptacle connector 1010.
The plug connector 1000 includes a cylindrical plug insulator 1001, and a plurality of contacts 1002 arranged on an outer surface of the plug insulator 1001 such that a distance from a distal end of the plug insulator 1001 to each of the contacts 1002 is different from others. The receptacle connector 1010 is formed with a hole 1011 into which the plug connector 1000 can be fit. The receptacle connector 1010 includes a plurality of circular receptacle contacts 1012 formed on an inner surface of the hole 1011.
FIG. 33 is a perspective view of the contact 1002. The contact 1002 is in shape of an arc, and is formed thereon centrally with a bead 1002a. The bead 1002a makes point-contact at a top thereof with the receptacle contact 1013 of the receptacle connector 1010.
FIG. 34 is a perspective view of another conventional electrical connector disclosed in Japanese Patent Application Laid-open on No. 2002-75558.
The illustrated electrical connector includes a receptacle connector sub-assembly 1110 and a plug connector sub-assembly 1120. The receptacle connector sub-assembly 1110 includes receptacle contacts 1101, 1102 and 1103 each including an elastic canti-lever 1104 having a contact 1104a. The receptacle contacts 1101, 1102 and 1103 are positioned in different locations in an axial direction of the receptacle connector sub-assembly 1110. The plug connector sub-assembly 1120 includes cylindrical plug contacts 1121, 1122 and 1123 each of which contacts each of the contacts 1104a. 
In the conventional electrical connector illustrated in FIG. 32, each of the contacts 1002 is formed in shape of an arc, and is formed centrally with the bead 1002a. However, since the beads 1002a merely contact the cylindrical receptacle contact 1013, it is unavoidable for the contacts 1002 to unstably contact the receptacle contact 1013.
The conventional electrical connector illustrated in FIG. 34 is accompanied with a problem that since arc surfaces of the contacts 1104a of the receptacle contacts 1101, 1102 and 1103 are convex in a direction perpendicular to a direction in which arc surfaces of the cylindrical plug contacts 1121, 1122 and 1123 extend, if a direction in which the receptacle contacts 1101, 1102 and 1103 extend is deviated from an axial direction of the cylindrical plug contacts 1121, 1122 and 1123, it is afraid that the contacts 1104a unstably contact the cylindrical plug contacts 1121, 1122 and 1123.
The contacts 1104a may be designed to have an arc surface extending along an arc surface of the cylindrical plug contacts 1121, 1122 and 1123. However, irregularity in each of the arc surfaces causes the arc surface of the contacts 1104a to incline, resulting in that it is quite difficult for the contacts 1104a to stably contact the cylindrical plug contacts 1121, 1122 and 1123.